JPH0640158A - Thermal recording material - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a heat-sensitive recording material having excellent recording sensitivity and light resistance of a recorded image. A thermosensitive recording medium in which an intermediate layer containing a pigment as a main component and a thermosensitive recording layer containing a color-forming agent and a color-forming agent that develops color by contacting with the color-forming agent are sequentially provided on a support. A heat-sensitive recording material containing microcapsules containing an ultraviolet absorber in a layer and having substantially no color forming ability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having excellent recording sensitivity and light resistance of a background portion and a printed portion.

[0002]

2. Description of the Related Art Thermosensitive recording media which are brought into contact with each other by heating to cause a contact reaction are well known. For example, there is a heat-sensitive recording material utilizing a color reaction between a colorless or light-colored basic dye and a color-developing agent. Since such a thermosensitive recording medium is relatively inexpensive, the recording device is compact, and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

For example, one of the fields of use thereof is a heat-sensitive recording label for a POS (point of sales) system of a retail store, etc. In addition to food labels that have completed their missions, the number of uses that are attached to products and used for a long period of time is increasing. However, in such applications, they are often exposed to water, wraps, oil, etc., and are often exposed to indoor light and sunlight for a long period of time, which causes the recorded image (printing) on the thermal label to fade. Defects such as yellowing of the background part are recognized, and as a result, the product image is significantly impaired.

In recent years, recording speeds of 10 seconds or less for an A4 size sheet for a thermal fax and 120 characters / second or more for a thermal printer have become possible, and there is a further demand for higher sensitivity of the thermal recording material. Conventionally, in order to obtain a high-sensitivity heat-sensitive recording material, it has been reported that the materials constituting the recording layer such as a coloring agent, a coloring agent and a sensitizer have been improved, or the base paper has been smoothed by blending the base paper or applying a pressure calender. Proposal to improve performance (Japanese Patent Publication No. 52-20142, Japanese Patent Publication No. 54-11525)
5, JP-A-53-156086), but none of them has been able to obtain satisfactory results because new defects are accompanied by improvements. For example, if the recording layer material is improved and the recording sensitivity is increased enough to react even with minute heat energy, the surface of the recording layer will be soiled before recording and the appearance will deteriorate, and smoothing treatment will also occur. By doing so, the heat insulating property of the base paper is lost, resulting in a problem such as poor sensitivity. For this reason, a method is generally used in which an intermediate layer containing a bulky pigment as a main component is provided between the support and the thermosensitive recording layer to increase the sensitivity. The provision of the layer has a drawback that the recorded image is easily discolored by exposure to light.

Therefore, for the purpose of improving this drawback, a method has been proposed in which a finely pulverized ultraviolet absorber is added to the protective layer provided on the heat-sensitive recording layer or to the heat-sensitive recording layer. Since the recording sensitivity is lowered by providing it, and because the finely pulverized ultraviolet absorber has a poor ultraviolet absorption efficiency, a sufficient effect cannot be obtained even if it is used in a small amount.
If it is used in a large amount in the heat-sensitive recording layer, new defects such as background fog or reduction in recording density occur.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermosensitive recording medium having excellent recording sensitivity and light fastness of recorded images.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have found that a heat-sensitive material containing, on a support, an intermediate layer containing a pigment as a main component, and a color-forming agent and a color-forming agent that develops a color by contacting with the color-forming agent. It has been found that the above object can be achieved by including microcapsules containing an ultraviolet absorber contained in the intermediate layer in the thermosensitive recording medium in which the recording layers are sequentially provided and which has substantially no color forming ability, and thus the present invention is completed. Came to do.

The present invention comprises a support and a heat-sensitive recording layer,
By providing an intermediate layer containing microcapsules containing a UV absorber that has virtually no color-developing ability, it has excellent recording sensitivity and yellowing of the background for a long time even when exposed to sunlight or indoor lighting. The present invention relates to a heat-sensitive recording material which is excellent in light resistance including print preservability. It is generally well known that an intermediate layer mainly composed of an oil-absorbing pigment is provided between the support and the heat-sensitive recording layer in order to increase the recording sensitivity of the heat-sensitive recording material. It is considered that, by providing the intermediate layer having the property, conversely, the reflected light increases and, as a result, the influence of the light on the thermosensitive recording layer increases.
Even if a protective layer is provided and the microcapsules according to the present invention are contained in the protective layer, sufficient light resistance can be obtained, but provision of the protective layer impairs heat conductivity to the heat-sensitive recording layer. As a result, it becomes difficult to obtain a heat-sensitive recording material having excellent target recording sensitivity.

[0009]

The present invention has a significant feature in that an intermediate layer containing a microcapsule containing a UV absorber and having substantially no color forming ability is provided. Various thermal recording media and pressure-sensitive recording media using microcapsules containing both a basic dye and an ultraviolet absorber have been proposed, but these microcapsules also contain a basic dye. In addition, not only the coloring phenomenon occurs with the increase of the light irradiation amount, but also the sufficient light resistance improving effect cannot be exhibited for a long period of time.

Specific examples of the ultraviolet absorber used in the present invention include the following. Salicylic acid type ultraviolet absorbers such as phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-
4-benzyloxybenzophenone, 2-hydroxy-
4-octyloxybenzophenone, 2-hydroxy-
4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-
Benzophenone-based UV absorbers such as hydroxy-4-methoxy-5-sulfobenzophenone, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole,
2- (2'-hydroxy-5'-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-
3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'- Hydroxy-3 ', 5'-di-tert
-Butylphenyl) -5-chlorobenzotriazole,
2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) benzotriazole, 2- [2'-hydroxy-3'-(3 ", 4", 5 ", 6" -tetrahydrophthalimide Methyl) -5'-methylphenyl] benzotriazole, 2- (2'-hydroxy-5'-tert-
Octylphenyl) benzotriazole, 2- [2'-
Hydroxy-3 ′, 5′-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2-
(2'-Hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-undecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy- 3'-undecyl-5'-methylphenyl) benzotriazole, 2-
(2'-Hydroxy-3'-tridecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tetradecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy- 3'-pentadecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-hexadecyl-
5'-methylphenyl) benzotriazole, 2-
[2'-hydroxy-4 '-(2 "-ethylhexyl)
Oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(2 "-ethylheptyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-
4 '-(2 "-ethyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-
(2 "-propyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(2"-
Propylheptyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(2 "-propylhexyl) oxyphenyl] benzotriazole, 2-
[2'-hydroxy-4 '-(1 "-ethylhexyl)
Oxyphenyl] benzotriazole, 2- [2'-hydroxy-4 '-(1 "-ethylheptyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-
4 '-(1 "-ethyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-
(1 ″ -propyloctyl) oxyphenyl] benzotriazole, 2- [2′-hydroxy-4 ′-(1 ″-
Propylheptyl) oxyphenyl] benzotriazole, 2- [2′-hydroxy-4 ′-(1 ″ -propylhexyl) oxyphenyl] benzotriazole, polyethylene glycol (molecular weight about 300) and methyl-3-
Condensation product with [3-tert-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate, 5-tert-butyl-3- (5-chloro-
Benzotriazole-based UV absorbers such as 2H-benzotriazol-2-yl) -4-hydroxybenzene-octyl propionate, 2'-ethylhexyl-2-cyano-3,3-diphenylacrylate, ethyl-2-cyano-3 , 3-Diphenyl acrylate and other cyanoacrylate UV absorbers, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, succinic acid-bis (2,2,6,6-tetramethyl-4) -Piperidyl)
Hindered amine UV absorbers such as esters and 2- (3,5-di-tert-butyl) malonic acid-bis (1,2,2,6,6-pentamethyl-4-piperidyl) ester.

Of course, the present invention is not limited to these, and two or more kinds may be used in combination if necessary. In the heat-sensitive recording material of the present invention, since the ultraviolet absorbent is used by being encapsulated in microcapsules, it is a low-melting ultraviolet absorbent which has been difficult to use in terms of background fog and storability, and at room temperature. Liquid UV absorbers can also be used,
The range of choice is greatly expanded.

Among these ultraviolet absorbers, the benzotriazole type ultraviolet absorbers which are liquid at room temperature are preferable because they can be included in the microcapsules at a high concentration as a core substance and have excellent ultraviolet absorbing ability. (2'-
Hydroxy-5'-tert-octylphenyl) benzotriazole, 2- [2'-hydroxy-3 ', 5'-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2'- Hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole,
2- (2'-hydroxy-3'-undecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-undecyl-5'-methylphenyl) benzotriazole, 2- (2'- Hydroxy-3'-tridecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tetradecyl-
5'-methylphenyl) benzotriazole, 2-
(2'-hydroxy-3'-pentadecyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-hexadecyl-5'-methylphenyl) benzotriazole, 2- [2'-hydroxy- 4'-
(2 ″ -ethylhexyl) oxyphenyl] benzotriazole, 2- [2′-hydroxy-4 ′-(2 ″ -ethylheptyl) oxyphenyl] benzotriazole,
2- [2'-hydroxy-4 '-(2 "-ethyloctyl) oxyphenyl] benzotriazole, 2- [2'
-Hydroxy-4 '-(2 "-propyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-(2" -propylheptyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy −
4 '-(2 "-propylhexyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-
(1 ″ -ethylhexyl) oxyphenyl] benzotriazole, 2- [2′-hydroxy-4 ′-(1 ″ -ethylheptyl) oxyphenyl] benzotriazole,
2- [2'-hydroxy-4 '-(1 "-ethyloctyl) oxyphenyl] benzotriazole, 2- [2'
-Hydroxy-4 '-(1 "-propyloctyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy-4'-(1" -propylheptyl) oxyphenyl] benzotriazole, 2- [2'-hydroxy −
4 '-(1 "-propylhexyl) oxyphenyl] benzotriazole, polyethylene glycol (molecular weight about 300) and methyl-3- [3-tert-butyl-5- (2
H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate condensate, 5-tert-butyl-3- (5-chloro-2H-benzotriazole-2
-Yl) -4-hydroxybenzene-octyl propionate is more preferably used because it exhibits a particularly remarkable effect of improving light resistance.

The amount of the ultraviolet absorber used is not particularly limited, but is 0.1 to 5.0 in the intermediate layer.
It is desirable to contain it in the range of g / m ² . When the amount of the ultraviolet absorber in the intermediate layer is less than 0.1 g / m ² , the ultraviolet absorption efficiency is lowered. On the other hand, if it exceeds 5.0 g / m ² , not only the effect of ultraviolet absorption becomes saturated, but also the intermediate layer inevitably becomes too thick, and the surface strength after coating the heat-sensitive recording layer (between the support and the coating layer) is increased. Adhesive strength) is reduced, and defects such as paper dust are generated.

The microcapsules used in the present invention can be prepared by various known methods. In general, cores obtained by dissolving a solid or liquid ultraviolet absorber at room temperature as described above in an organic solvent as needed. It is prepared by a method in which a substance is emulsified and dispersed in an aqueous medium to form a wall film made of a polymer substance around oily droplets. Specific examples of the polymer substance that forms the wall film of the microcapsule include, for example, polyurethane resin, polyurea resin, polyamide resin, polyester resin, polycarbonate resin, aminoaldehyde resin,
Examples thereof include melamine resin, polystyrene resin, styrene-acrylate copolymer resin, styrene-methacrylate copolymer resin, gelatin and polyvinyl alcohol.

Among these, the microcapsules having a wall film made of a polyurethane polyurea resin or an aminoaldehyde resin are particularly excellent in heat resistance and have an excellent accompanying effect of improving the heat insulating property which is the original purpose of the intermediate layer. In addition, it has a spherical shape compared to other microcapsules composed of other wall films and ordinary pigments. Therefore, when blended in the intermediate layer, the smoothness of the intermediate layer smeared surface is further improved. It is preferably used because the sensitivity can be increased.

Microcapsules having a wall film made of polyurethane / polyurea resin are a core substance for encapsulating a capsule wall film material such as a polyvalent isocyanate and a polyol which reacts therewith, or an adduct of a polyvalent isocyanate and a polyol. It is produced by emulsifying and dispersing it in an aqueous medium in which a protective colloid substance such as polyvinyl alcohol is dissolved and raising the liquid temperature to cause a polymer forming reaction at the oil drop interface.

Examples of the polyvalent isocyanate compound include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate,
2,4-tolylene diisocyanate, naphthalene-1,
4-diisocyanate, diphenylmethane-4,4'-
Diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4
-Diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1, Diisocyanates such as 4-diisocyanate, 4,4 ′, 4 ″ -triphenylmethane triisocyanate, triisocyanates such as toluene-2,4,6-triisocyanate, 4,4′-dimethyldiphenylmethane-2,2 ′ , 5,5'-Tetraisocyanate and other tetraisocyanates, addition product of hexamethylene diisocyanate and trimethylolpropane, addition of 2,4-tolylene diisocyanate and trimethylolpropane , An adduct of xylylene diisocyanate and trimethylolpropane, an isocyanate prepolymer of adduct of trimethylolpropane resin isocyanate and hexane triol.

Examples of the polyol compound include ethylene glycol, 1,3-propanediol, 1,4
-Butanediol, 1,5-pentanediol, 1,6
-Hexanediol, 1,7-heptanediol, 1,
8-octanediol, propylene glycol, 2,3
-Dihydroxybutane, 1,2-dihydroxybutane,
1,3-dihydroxybutane, 2,2-dimethyl-1,
3-propanone diol, 2,4-pentane diol,
2,5-hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol,
Dihydroxycyclohexane, diethylene glycol,
1,2,6-trihydroxyhexane, phenylethylene glycol, 1,1,1-trimethylolpropane,
Aromatic polyols such as hexanetriol, pentaerythritol and glycerin, aromatic polyhydric alcohols such as 1,4-di (2-hydroxyethoxy) benzene and 1,3-di (2-hydroxyethoxy) benzene, and alkylene oxides Condensation product, p-xylylene glycol, m-xylylene glycol, α, α′-dihydroxy-p-diisopropylbenzene, 4,4′-dihydroxydiphenylmethane, 2- (p, p′-dihydroxydiphenylmethyl) benzyl alcohol 4,4'-isopropylidenediphenol, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, ethylene oxide adduct of 4,4'-isopropylidenediphenol, 4,4'-isopropylidene Of ridenediphenol Examples include propylene oxide adducts.

Of course, the polyisocyanate compound and the polyol compound are not limited to the above compounds, and two or more kinds may be used in combination, if necessary. Among the polyvalent isocyanate compounds used in the present invention or the adducts of the polyvalent isocyanate compounds and the polyol compounds, those having three or more isocyanate groups in the molecule are particularly preferable.

The microcapsules having a wall film made of an aminoaldehyde resin are manufactured by a formulation in which the wall film material is added after emulsifying the core substance, so that the thickness of the wall film can be controlled regardless of the particle size of the emulsion. The merit that can be done is also demonstrated.
Capsules having an aminoaldehyde resin wall film generally include at least one amine such as urea, thiourea, alkylurea, ethyleneurea, acetoguanamine, benzoguanamine, melamine, guanidine, biuret, and cyanamide, and formaldehyde, acetaldehyde, and paraformaldehyde. , Hexamethylenetetramine, glutaraldehyde, glyoxal, furfural and the like, or an in-situ polymerization method using an initial condensate obtained by condensing them.

Milk used for microencapsulation
As an agent (protective colloid agent), various anions and
Nion, cation or amphoteric water-soluble polymer compound etc. are used
To be done. Examples of the anionic polymer compound include -C
OO^-, -SO^3- , -OPO₃ ^2- Arabic with groups etc.
Gum, carrageenan, sodium alginate, pectic acid,
Natural high content such as tragacanth gum, almond gum and agar
Child compound, carboxymethyl cellulose, sulfated cellulosics
Glucose, sulfated methyl cellulose, carboxymethylated starch
Semi-synthetic high content of powder, phosphorylated starch, lignin sulfonic acid, etc.
Child compound, maleic anhydride (including hydrolyzed ones)
Copolymer, acrylic acid, methacrylic acid or croton
Acid polymers and copolymers, vinylbenzene sulfonic acid
Ruiya 2-acrylamido-2-methylpropanesulfone
Acid polymers and copolymers, and these polymers or
Partial amide derivative or partial esterified product of copolymer,
Carboxy modified polyvinyl alcohol, sulfonic acid modified
Polyvinyl alcohol, phosphoric acid modified polyvinyl alcohol
Synthetic polymer compounds such as styrene and the like are included. More specifically
Is a maleic anhydride (including hydrolyzed) copolymerization
As the body, methyl vinyl ether-maleic anhydride
Polymer, ethylene-maleic anhydride copolymer, styrene
-Maleic anhydride copolymer, α-methylstyrene-anhydrous
Maleic acid copolymer, vinyl acetate-maleic anhydride copolymer
Coalesce, methacrylamide-maleic anhydride copolymer, a
Sobutylene-maleic anhydride copolymer and the like can be mentioned.
Acrylic acid copolymer, methacrylic acid copolymer or black
As the tonic acid copolymer, methyl acrylate-acrylic
Acid copolymer (hereinafter abbreviated as "copolymer"), acrylic acid ester
Chill-acrylic acid, methyl acrylate-methacrylic acid,
Methyl methacrylate-acrylic acid, methyl methacrylate
-Methacrylic acid, methyl acrylate-acrylamide-
Acrylic acid, acrylonitrile-acrylic acid, acrylo
Nitrile-methacrylic acid, hydroxyethyl acrylate
To-acrylic acid, hydroxyethylmethacrylate
Tacrylic acid, vinyl acetate-acrylic acid, vinyl acetate-medium
Tacrylic acid, acrylamide-acrylic acid, acrylic acid
Mido-methacrylic acid, methacrylamide-acrylic acid,
Methacrylamide-methacrylic acid, vinyl acetate-crot
Copolymers such as acid, vinylbenzene sulfone
Acid or 2-acrylamido-2-methyl-propane
As the sulfonic acid copolymer, methyl acrylate-vinyl chloride
Rubenzenesulfonic acid (or its salt) copolymer, vinyl acetate
Nyl-vinylbenzene sulfonic acid copolymer, acrylic
Mido-vinylbenzene sulfonic acid copolymer, Acryloy
Rumorpholine-vinylbenzene sulfonic acid copolymer, vinyl
Nylpyrrolidone-vinylbenzene sulfonic acid copolymer,
Vinylpyrrolidone-2-methyl-propanesulfonic acid
Examples thereof include polymers.

Examples of the nonionic polymer compound include semi-synthetic polymer compounds such as hydroxyethyl cellulose, methyl cellulose, pullulan, soluble starch, and oxidized starch having a —OH group, and synthetic polymer compounds such as polyvinyl alcohol. Examples of the cationic polymer compound include cation-modified polyvinyl alcohol and the like. Examples of the amphoteric polymer compound include gelatin and the like.

Although the amount of the emulsifier used is not particularly limited, in general, when the polyurethane / polyurea resin is used as the wall film material, the total of the wall film material, the ultraviolet absorber and the organic solvent is used. However, it may be adjusted in the range of 1 to 50% by weight, preferably 3 to 30% by weight. When the aminoaldehyde resin is used as the wall film material, the amount of the emulsifier used is the hydrophobic core substance 100.
It is prepared in an amount of 1 to 20 parts by weight, preferably 3 to 10 parts by weight, based on parts by weight.

The organic solvent is not particularly limited and can be appropriately selected from various high boiling point hydrophobic media used in the field of pressure-sensitive copying paper, and specifically, for example, phosphoric acid can be used. Phosphates such as tricresyl, octyldiphenyl phosphate, dibutyl phthalate,
Phthalates such as dioctyl phthalate, carboxylic esters such as butyl oleate, various fatty acid amides, alkylated naphthalenes such as diethylene glycol dibenzoate, monoisopropyl naphthalene and diisopropyl naphthalene, 1-methyl-1-phenyl- 1-
Alkylated benzenes such as tolylmethane, 1-methyl-1-phenyl-1-xylylmethane, 1-phenyl-1-tolylmethane, alkylated biphenyls such as isopropyl biphenyl, xenoxyalkanes such as o-phenylphenol glycidyl ether, Examples thereof include acrylic acid esters such as trimethylolpropane triacrylate, esters of polyhydric alcohols and unsaturated carboxylic acids, chlorinated paraffins, and kerosene. Of course, these may be used in combination of two or more kinds. Further, generally, the lower the viscosity of the mixture of the capsule wall film material, the ultraviolet absorber and the organic solvent, the smaller the particle size after emulsification and the sharper the particle size distribution. Therefore, if necessary, the viscosity of the mixture is decreased. A low boiling point solvent may be used together for the purpose. Specific examples of such a low boiling point solvent include ethyl acetate, butyl acetate, methylene chloride and the like.

The amount of the organic solvent used is not particularly limited and should be appropriately adjusted according to the type and amount of the ultraviolet absorber used, the type of the organic solvent and the like. However, since it is preferable that the ultraviolet absorbent is sufficiently dissolved in the microcapsules, in the case of polyurethane / polyurea resin, the total amount of the organic solvent, the ultraviolet absorbent and the microcapsule wall film material is Therefore, it is desirable to adjust the ratio of the organic solvent to be in the range of generally 10 to 60% by weight, preferably 20 to 60% by weight. In the case of amino aldehyde resin,
It is desirable to adjust the content of the ultraviolet absorber in the range of 50 to 2000% by weight, preferably 100 to 1000% by weight. In addition, when the ultraviolet absorber which is liquid at room temperature is used, the organic solvent is not always essential, and may be appropriately adjusted within the above range as necessary.

Although the amount of the capsule wall film material used is not particularly limited, the organic solvent in the microcapsules may exude due to long-term storage, which may deteriorate the storability of the thermosensitive recording medium. It is preferable to use a larger amount of wall film material than the microcapsules, and in the case of polyurethane / polyurea resin, the wall film is used for the total of the organic solvent, the ultraviolet absorber and the microcapsule wall film material. 20% to 70% by weight, preferably 2
It is desirable to select it so as to be in the range of 5 to 60% by weight. In the case of aminoaldehyde resin, the wall film material is 30 to 300 with respect to the total amount of the ultraviolet absorber and the organic solvent used as necessary. % By weight, preferably 35-200% by weight
It is desirable to select the range so that

Further, the amount of the ultraviolet absorbent used in the microencapsulation should be appropriately selected according to the kind of the ultraviolet absorbent and the organic solvent used and is not particularly limited, but a remarkable effect is obtained. Therefore, in the case of polyurethane / polyurea resin, the amount of the ultraviolet absorber is about 3 to 80% by weight, preferably about 5 to 70% by weight, based on the total of the organic solvent, the ultraviolet absorber and the microcapsule wall membrane material. It is desirable to mix so that
In the case of an aminoaldehyde resin, it is 3 to 75% by weight, preferably 3 to 75% by weight based on the total of the ultraviolet absorber, the microcapsule wall film material, and the organic solvent used as necessary.
It is desirable to mix them so that the amount of the ultraviolet absorber is about 50% by weight.

In the microcapsule used in the present invention, an antioxidant, an oil-soluble fluorescent dye, a release agent and the like can be added, if necessary, in addition to the ultraviolet absorber. Further, at the time of microencapsulation, a tin compound, a polyamide compound, an epoxy compound, a polyamine compound or the like can be used together as a reaction accelerator. When a polyamine compound is used, it is desirable to use an aliphatic polyamine compound from the viewpoint of light resistance.

The average particle size of the microcapsules used in the present invention is preferably adjusted in the range of 0.1 to 3 μm in consideration of the absorption efficiency of ultraviolet rays and the quality of recorded images.
Further, the amount of the microcapsules to be added to the intermediate layer should be appropriately selected depending on the type of the ultraviolet absorber, the concentration in the capsules, the desired quality, and the like.
It is desirable to adjust the amount in the range of 10 to 120% by weight, preferably 20 to 100% by weight, based on the solid pigment amount of the intermediate layer.

The intermediate layer in the present invention is mainly composed of a pigment, and examples of such a pigment include calcined kaolin, aluminum silicate, calcium silicate, magnesium silicate,
Known materials such as magnesium aluminosilicate, amorphous silica, and titanium oxide can be appropriately used, but are not limited to these, and in consideration of the influence on the thermal recording head, JI
Oil absorption by SK-5101 method is 80ml / 100g
The above is desirable.

Various known adhesives may be used as the adhesive for the intermediate layer. Specific examples include natural rubber, polybutadiene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, methylmethacrylate-butadiene copolymers, 2-vinylpyridine-styrene-butadiene copolymers, acrylate polymers. Copolymers, acrylate-styrene copolymers, latexes such as vinyl chloride copolymers, oxidized starch, enzyme-modified starch cationic starch, esterified starch, starches such as etherified starch, methyl cellulose, ethyl cellulose,
Cellulose such as carboxymethyl cellulose, methoxy cellulose, hydroxyethyl cellulose, completely (or incompletely) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyvinyl alcohol such as acetoacetylated polyvinyl alcohol, sodium polyacrylate, polyacrylamide, polyvinylpyrrolidone , Acrylic acid amide / acrylic acid ester copolymer,
Water-soluble polymers such as acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, sodium alginate, gelatin, casein, etc. However, the present invention is not limited to these. If necessary, various auxiliary agents such as a dispersant, a defoaming agent, a coloring dye and a fluorescent dye can be appropriately added to the coating liquid for the intermediate layer.

The intermediate layer coating solution prepared by mixing the coating composition is
A coating device used for producing a general coated body on a support, eg
For example, blade coater, roll coater, reverse low
Le Coater, Rod Blade Coater, Champlek
It is applied by a scorch coater coater or the like.
The coating amount of the intermediate layer is 1 to 20 g / m 2 as dry weight. ²
Is preferable, and more preferably 2 to 12 g / m.²Extent of degree
It is adjusted as appropriate.

The thermosensitive recording medium of the present invention is produced by providing a thermosensitive recording layer on the intermediate layer thus formed, and various combinations can be applied as the color-forming substance constituting the recording layer. Specifically, the following are exemplified. (a) As described in JP-B-41-14510,
Melting point having secondary alcoholic hydroxyl group 100-180
A combination consisting of a compound at 0 ° C., sulfur and metal inorganic salts or metal acetates. Here, as the compound having a secondary alcoholic hydroxyl group, a benzoin compound such as benzoin, 2-methoxybenzoin, 4-chlorobenzoin, 4-dimethylaminobenzoin, 2-chloro-4'-dimethylaminobenzoin, diphenylcarbinol, etc. Carbinols such as, resorcin, pyrogallol, 3
-Hydroxytoluene-4-sulfonic acid, 4-nitroresorcin, phenolic compounds such as 4,6-dibromoresorcin, and fatty acid polyhydric alcohols such as erythritol, sorbitol, galactase, maltose, mannitol and saccharose. To be The metal inorganic salts and metal acetates include many of the metals that react with hydrogen sulfide to produce colored sulfides, such as copper, lead tin, molybdenum, cobalt, chromium, nickel, manganese, and titanium. , Antimony, rhodium, osmium, mercury, iron, barium, bismuth, arsenic, magnesium, indium and iridium.

(B) A combination in which various inorganic metal salts in the composition (a) described in JP-B No. 41-14511 are replaced with hexamethylenetetramine / metal salt adducts. (c) Described in Japanese Examined Patent Publication No. 42-13237,
A combination of carbohydrates and dehydrating agents. Here, examples of the carbohydrate include saccharose, fructose, galactose, starch, and the like, and examples of the dehydrating agent include sulfuric acid, acetic anhydride, anhydrous zinc chloride, paratoluenesulfonic acid, and the like. (d) Combination of long-chain fatty acid iron salts such as ferric stearate and ferric myristate with phenols such as tannic acid, gallic acid and ammonium salicylate.

(E) Organic heavy metal salts such as nickel, cobalt, lead, copper, iron, mercury and silver salts such as acetic acid, stearic acid and palmitic acid, and alkaline earth metal sulfides such as calcium sulfide, strontium sulfide and barium sulfide. Or a combination of the organic acid heavy metal salt and an organic chelating agent such as S-diphenylcarbazide and diphenylcarbazone. (f) A combination of a heavy metal oxalate such as silver, lead, mercury or thorium oxalate and a sulfur compound such as Na-tetrathionate, sodium thiosulfate or thiourea. (g) ferric stearate such as ferric stearate and ferric salt of 3,4
In combination with an aromatic polyhydroxy compound such as dihydroxytetraphenylmethane. (h) A combination of an organic acid noble metal such as silver oxalate or mercury oxalate and an organic polyhydroxy compound such as polyhydroxy alcohol, glycerin or glycol.

(I) A combination of an organic acid noble metal salt such as silver behenate or silver stearate and an aromatic organic reducing agent such as protocatechuic acid, spiroindane or hydroquinone. (j) A combination of a ferric fatty acid salt such as ferric pelargonate and ferric lauric acid with a thiosemicarbazide or isothiosemicarbazide derivative. (k) A combination of an organic acid lead salt such as lead caproate, lead pelargonate or lead behenate and a thiourea derivative such as ethylene thiourea or N-dodecyl thiourea. (l) A combination of a higher fatty acid heavy metal salt such as ferric stearate or copper stearate and zinc dialkyldithiocarbamate. (m) A compound which forms an oxazine dye, such as a combination of resorcin and a nitroso compound, or a compound which forms an azo dye. (n) A compound that forms an azo dye, such as a combination of a diazonium salt and a coupler compound. (o) A combination of a colorless or pale basic dye such as crystal violet lactone and a color former such as bisphenol A. (p) JP-A-58-38733 and JP-A-60-26
A combination utilizing a color reaction between an imino compound and an isocyanate compound described in JP-A-2686.

Among the various combinations described above, a combination of a colorless or light-colored basic dye and a coloring agent is most preferably used, and therefore, a more detailed description will be given below. As the basic dye, various known colorless or light-colored basic dyes can be used, and specifically, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide and 3- (4 -Diethylamino-2-methylphenyl)
-3- (4-Dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [a] fluorane, 3- (N-ethyl-
N-p-tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,6-bis (diethylamino) fluorane -Γ
-Anilinolactam, 3-cyclohexylamino-6-
Chlorofluorane, 3-diethylamino-6-methyl-
7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N
-Methyl-N-cyclohexyl) amino-6-methyl-
7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n-butyl)
Amino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3- Di (n-butyl) amino-7- (o-chlorophenylamino) fluorane, 3-
Diethylamino-7- (o-fluorophenylamino)
Fluorane, 3-di (n-butyl) amino-7- (o-
Fluorophenylamino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p- Truizino) Fluoran, 3- (N-
Ethyl-N-furfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-
7-anilinofluorane, 3- (N-methyl-Nn-)
Propylamino) -6-methyl-7-anilinofluorane, 3,3-bis [1- (4-methoxyphenyl) -1
-(4-Dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3
-Bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,
6,7-Tetrachlorophthalide, 3,3-bis [1,1
-Bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3-p
-(P-anilinoanilino) anilino-6-methyl-7
-Chlorofluorane, 2,2-bis {4- [6 '-(N
-Cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] phenyl} propane, 3,6, -bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide and the like can be mentioned. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Various materials are known for the color former used in combination with the basic dye as described above, and examples thereof include the following. Inorganic acidic substances such as activated clay, attapulgite, colloidal silica, aluminum silicate,
4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert-octylcatechol, 2,2′-dihydroxydiphenol, 4,4′-
Isopropylidene bis (2-tert-butylphenol), 4,4'-sec-butylidene diphenol, 4-
Phenylphenol, 4,4'-isopropylidenediphenol (bisphenol A), 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 2,2'-
Methylenebis (4-chlorophenol), hydroquinone, 4,4'-cyclohexylidenediphenol, 4,
4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,4
4'-trihydroxybenzophenone, 2,2 ', 4
4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate,
Propyl 4-hydroxybenzoate, sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, 4
-Chlorophenyl hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, -p-chlorobenzyl 4-hydroxybenzoate, -p-methoxybenzyl 4-hydroxybenzoate,
Phenolic compounds such as novolac type phenol resin and phenol polymer, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-
Aromatic carboxylic acids such as 4-hydroxybenzoic acid and 3,5-dimethyl-4-hydroxybenzoic acid, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-
Isopropyloxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 3,4-dihydroxydiphenyl sulfone, 3,4- 4-hydroxydiphenylsulfone derivative such as dihydroxy-4'-methyldiphenylsulfone, bis (3-tert-butyl-4-hydroxy-6-methylphenyl) sulfide, bis (2-methyl-4-hydroxy-6-tert-) Sulfide derivatives such as butylphenyl) sulfide, and further these phenolic compounds, 4- [2- (p-methoxyphenoxy)
Ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p-
Aromatic carboxylic acids such as (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, and these aromatic carboxylic acids and the like with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel. Examples thereof include salts, and organic acid substances such as antipyrine complex of zinc thiocyanate.

The use ratio of the basic dye and the color developing agent is appropriately selected according to the type of the basic dye or the color developing agent to be used and is not particularly limited, but in general, the basic dye 1 is used. 1 to 50 parts by weight, preferably 2 to parts by weight
About 10 parts by weight of coloring agent is used. The coating material for a heat-sensitive recording layer containing a basic dye and a colorant in the present invention is generally prepared by dispersing water together as a dispersion medium, together or separately by a stirring / grinding machine such as a ball mill, attritor, or sand mill. To be done.

In the coating liquid, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol, etc. Diisobutylene / maleic anhydride copolymer salt, styrene /
Maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene /
At least one of butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin and the like is blended in an amount of 5 to 40% by weight, preferably 15 to 30% by weight, based on the total solid content of the recording layer. To be done.

If desired, various auxiliary agents can be added to the coating liquid. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts. , Zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and other waxes,
An antifoaming agent, a fluorescent dye, a coloring dye, etc. are appropriately added. Further, the microcapsules containing the ultraviolet absorbent of the present invention may be blended in the recording layer coating liquid to further enhance the light resistance.

It is also possible to use various pigments in combination in the coating liquid, for example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth,
Inorganic pigments such as fine particulate anhydrous silica and activated clay, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles can be used.

Further, a sensitizer may be used in combination depending on the purpose. Specific examples of the sensitizer include stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebistearic acid amide, behenic acid amide, and methylenebisstearic acid amide. , N-methylol stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate,
Benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p- Chlorobenzyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane,
1,2-di (4-methylphenoxy) ethane, 1,2-
Di (4-methoxyphenoxy) ethane, 1,2-di (4
-Chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p
-Acetotoluidide, p-acetophenetidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like are exemplified. To be done. The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within the range of about 4 parts by weight or less relative to 1 part by weight of the color developing agent.

Further, a preservative improving agent may be used in combination for the purpose of further enhancing preservability of a recorded image as long as the effect is not impaired. Specific examples of such a storage stability improver include, for example, 2,2'-methylenebis (4-methyl-6).
-Tert-butylphenol), 2,2'-ethylenebis (4-methyl-6-tert-butylphenol) 2,2 '
-Methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4,6-di-tert-
Butylphenol), 2,2'-ethylidene bis (4,
6-di-tert-butylphenol), 2,2'-ethylidenebis (4-methyl-6-tert-butylphenol), 2,2'-ethylidenebis (4-ethyl-6-te)
rt-Butylphenol), 2,2 '-(2,2-propylidene) bis (4,6-di-tert-butylphenol), 2,2'-methylenebis (4-methoxy-6-te)
rt-butylphenol), 2,2'-methylenebis (6
-Tert-butylphenol), 4,4'-thiobis (3
-Methyl-6-tert-butylphenol), 4,4'-
Thiobis (2-methyl-6-tert-butylphenol), 4,4'-thiobis (5-methyl-6-tert-butylphenol), 4,4'-thiobis (2-chloro-)
6-tert-butylphenol), 4,4'-thiobis (2-methoxy-6-tert-butylphenol), 4,
4'-thiobis (2-ethyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-) 5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4′-thiobis (3-methylphenol), 4,4′- Dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3', 5,5'-
Tetramethyldiphenyl sulfone, 2,2-bis (4-
Hydroxy-3,5-dibromophenyl) propane,
2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,
Hindered phenol compounds such as 5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene,
Epoxy compounds such as 4,4′-diglycidyloxydiphenyl sulfone, diglycidyl terephthalate, and bisphenol A type epoxy resin, 1- [α-methyl-α-
(4'-Hydroxyphenyl) ethyl] -4- [α ',
α'-bis (4 "-hydroxyphenyl) ethyl] benzene, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di-tert-
Butylphenyl) sodium phosphate and the like.

If necessary, microcapsules containing the above-mentioned UV absorber may be contained in the heat-sensitive recording layer, between the intermediate layer and the heat-sensitive recording layer, or in the protective layer provided on the heat-sensitive recording layer. Is also possible. Further, various known techniques in the field of producing a heat-sensitive recording material, such as a pressure-sensitive adhesive treatment on the back surface of the recording material and an adhesive label processing, can be added as necessary.

The method for applying the recording layer is not particularly limited, and it can be formed according to a conventionally well-known and commonly used technique. For example, bar coating, air knife coating, rod blade coating, pure blade coating, short dwell coating, It is formed by a method of applying and drying a coating liquid by varibar blade coating, curtain coating, die coating, or the like. The coating amount of the coating liquid is also not particularly limited, but is usually 2 to 12 g / dry weight.
m ² , preferably in the range of about 3 to 10 g / m ² .

In the thermosensitive recording medium of the present invention, the support is not particularly limited, and may be appropriately selected from paper, plastic film, synthetic paper, non-woven fabric, metal vapor deposition and the like.

[0048]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 Preparation of Liquid A In a stirring and mixing container equipped with a heating device, 8 parts of polyvinyl alcohol [trade name: PVA-217EE, manufactured by Kuraray Co., Ltd.] were used.
% Aqueous solution 60 parts was added to make an aqueous medium for producing microcapsules.

Separately, in 12 parts of tricresyl phosphate, 2-
(2'-Hydroxy-5'-methylphenyl) benzotriazole [Product name: Sumizob 200, Sumitomo Chemical Co., Ltd.]
2 parts, xylylene diisocyanate and trimethylolpropane (3: 1) adduct [trade name: Takenate D-1
10N, Takeda Pharmaceutical Co., Ltd., containing 25% of ethyl acetate] 18 parts was dissolved to obtain a solution, which was then added to the TK homomixer [Model HV-M, Tokushu Kika Kogyo Co., Ltd.] in the above aqueous medium for capsule production. ] Was emulsified and dispersed while cooling so that the average particle diameter was 2 μm. Next, 50 parts of water was added to this emulsified dispersion and reacted at 60 ° C. for 3 hours with stirring to prepare a microcapsule dispersion having a wall film made of a polyurethane / polyurea resin containing an ultraviolet absorber.

Formation of Intermediate Layer Calcined Kaolin [Product Name: Ansilex, manufactured by EMC]
100 parts and 8 parts of 50% styrene-butadiene copolymer latex were prepared so as to have a solid content of 44%, treated with a disperser to obtain a pigment dispersion, and then 400 parts of solution A,
50 g / m of an intermediate layer coating liquid obtained by mixing and stirring 20 parts of 10% polyvinyl alcohol and 1 part of 5% methyl cellulose.
^{The high-} quality paper of No. ² was coated and dried with a rod blade coater so that the coating amount after drying was 8 g / m ² , to obtain an intermediate-layer coated paper.

Preparation of Solution B 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 10 parts, 1,2-di (3-methylphenoxy) ethane 20 parts, 5% aqueous solution of methylcellulose 10
Parts and 30 parts of water were pulverized with a sand mill until the average particle size became 0.9 μm.

Preparation of Liquid C A composition consisting of 30 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone, 30 parts of a 5% aqueous solution of methylcellulose, and 40 parts of water was pulverized with a sand mill until the average particle size became 1.1 μm. did.

Formation of Recording Layer Liquid B 70 parts, liquid C 80 parts, calcium carbonate 15 parts, 30
% Zinc stearate dispersion 3 parts, 20% oxidized starch aqueous solution 15 parts, 10% polyvinyl alcohol aqueous solution 50 parts,
24 parts of water was mixed and stirred to obtain a recording layer coating liquid. The resulting coating liquid was applied onto the intermediate layer so that the coating amount after drying was 6 g / m ^2, and dried to form a thermosensitive recording layer. Then, a super calender process was performed to obtain a thermosensitive recording medium.

Example 2 In the preparation of solution A of Example 1, 3 parts of ethyl acetate and 2 parts of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole were used instead of 12 parts of tricresyl phosphate. Instead, 2- (2'-
Hydroxy-3'-dodecyl-5'-methylphenyl)
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 12 parts of benzotriazole [trade name: Tinuvin 171, manufactured by Ciba Geigy] was used.

Example 3 In the preparation of solution A of Example 2, instead of 18 parts of the (3: 1) adduct of xylylene diisocyanate and trimethylolpropane, hexamethylene diisocyanate trimer (isocyanurate type) [ Trade name: Takenate D-170HN, manufactured by Takeda Pharmaceutical Co., Ltd.] 18 parts was used, and a thermosensitive recording medium was obtained in the same manner as in Example 2 except that the reaction conditions were changed from 60 ° C. for 3 hours to 90 ° C. for 5 hours. It was

Example 4 Preparation of Liquid D In a stirring and mixing vessel equipped with a heating device, 150 parts of a 5% aqueous solution of polyacrylic acid was added, and the pH of the system was adjusted to 4.5 to prepare an aqueous medium for capsule production. And Separately, ethyl acetate 2
2- (2'-hydroxy-3'-dodecyl-5 'in 0 part
-Methylphenyl) benzotriazole (96 parts) was dissolved in the above-mentioned aqueous medium for capsule production using a TK homomixer [Model HV-M, manufactured by Tokushu Kika Kogyo Co., Ltd.] as a capsule core substance while cooling at 10,000 rpm. And emulsified and dispersed for 15 minutes. To this emulsion dispersion, 190 parts of a 30% aqueous solution of a commercially available melamine-formaldehyde initial condensate was added as a wall film material, and the mixture was reacted at 90 ° C. for 3 hours while continuing stirring, and then the temperature was lowered to room temperature to obtain an ultraviolet absorber. A melamine-formaldehyde resin wall membrane capsule having an average particle diameter of 2 μm was prepared. Formation of Recording Layer Hereinafter, a thermosensitive recording medium was obtained in the same manner as in Example 1 except that 250 parts of D liquid and 150 parts of water were used in place of 400 parts of A solution in the formation of the intermediate layer of Example 1. .

Example 5 In the preparation of solution D, after reacting at 90 ° C. for 3 hours, the pH was lowered to 3.5 and further 80 ° C.
After stirring and keeping the temperature for 3 hours, cool and average particle size 2.5μ
A thermosensitive recording medium was obtained in the same manner as in Example 4, except that a melamine-formaldehyde resin wall membrane capsule of m was prepared and the coating liquid for the intermediate layer was prepared.

Comparative Example 1 In the preparation of solution A, 2-
A thermal recording material was obtained in the same manner as in Example 1 except that 2 parts of (2'-hydroxy-5'-methylphenyl) benzotriazole was not used.

Comparative Example 2 Liquid A 4 was used in the formation of the intermediate layer.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 00 part was not added.

Comparative Example 3 Preparation of Solution 7E 10 parts of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole 5% 5% aqueous solution of methylcellulose
Parts and 20 parts of water were pulverized with a sand mill so that the average particle diameter was 1.5 μm. A thermosensitive recording medium was obtained in the same manner as in Example 2 except that 100 parts of the E liquid was used instead of 400 parts of the A liquid in the formation of the intermediate layer.

[Comparative Example 4]
(2'-Hydroxy-5'-methylphenyl) benzotriazole Instead of 10 parts of 2- (2'-hydroxy-
A thermosensitive recording medium was obtained in the same manner as in Comparative Example 3 except that 10 parts of 3 ', 5'-di-tert-aminophenyl) benzotriazole was used.

Comparative Example 5 The thermal recording layer prepared in Example 1 was applied directly to a high-quality paper of 50 g / m ² without forming an intermediate layer to form a thermal recording layer, and a super calender treatment was carried out in the same manner. Then, a thermosensitive recording medium was obtained.

The following 10 evaluation tests were carried out on the 10 kinds of thermal recording materials thus obtained, and the results are shown in [Table 1]. [Evaluation] 1 [Coloring property] Using a heat-sensitive evaluation machine [trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.], applied voltage 24 V, applied energy 0.21 mj /
Each thermosensitive recording medium was color-developed at dot and 0.43 mj / dot, and the color density of the obtained recorded image was measured by a Macbeth densitometer [RD-914 type, manufactured by Macbeth Co.] in a visual mode. 2 [Light resistance] The initial density of the background and recording areas of the thermosensitive recording medium after recording in 1 above and the recording density after exposure to direct sunlight for 2 days were measured with a Macbeth densitometer (using a blue filter). 3 [Background fog] The thermal density of the heat-sensitive recording material after recording in 1 above was left for 24 hours at 50 ° C. and 75% RH, and the background density was measured with a Macbeth densitometer (visual mode). The background fog was evaluated.

[0065]

[Table 1]

[0066]

As is clear from the results of [Table 1], all of the heat-sensitive recording materials of the present invention have excellent recording sensitivity, and have very little light resistance to fading of recorded images and background fog even when exposed to light. It was an excellent thermal recording material.

Claims (4)

[Claims] 1. A thermosensitive recording medium comprising, on a support, an intermediate layer containing a pigment as a main component, and a thermosensitive recording layer containing a color former and a color former which develops color when contacting with the color former in order. 2. A heat-sensitive recording material characterized in that the intermediate layer contains microcapsules containing an ultraviolet absorber and having substantially no color-forming ability. 2. The average particle size of the microcapsules is 0.1 to 10.
The thermosensitive recording medium according to claim 1, which has a thickness of 3 μm. 3. The microcapsule having a wall film made of a polyurethane polyurea resin or an aminoaldehyde resin, according to claim 1 or 2.
The heat-sensitive recording material described. 4. The heat-sensitive recording material according to claim 1, wherein the ultraviolet absorber is a benzotriazole derivative which is liquid at room temperature.